Pressure multiple electrical contact assembly for electrical devices



Dec. 12, 1967 J. J. STEINMETZ, JR. E TAL 3,358,196 PRESSURE MULTIPLEELECTRICAL CONTACT ASSEMBLY FOR ELECTRICAL DEVICES Filed June 8 1966 2Sheets-Sheet 1 FIG.4.

WITNESSES INVENTORS John J. Sfeinmefz,Jr 8 a K (AA/aw Pasquale A.TrongoB Y '27 2% M ATTmEY Dec. 12, 1967 J. J. STEINMETZ, JR, ETAL 3,358,196PRESSURE MULTIPLE ELECTRICAL CONTACT ASSEMBLY FOR ELECTRICAL DEVICESFiled June 8 1966 2 Sheets-Sheet 2 United States Patent 3,358,196PRESSURE MULTIPLE ELECTRICAL CONTACT ASSEMBLY FOR ELECTRICAL DEVICESJohn J. Steinmetz, In, Monroeville, and Pasquale A.

Trongo, Greenshurg, Pa, assignors to Westinghouse Electric Corporation,Pittsburgh, Pa., a corporation of Pennsylvania Filed June 8, 1966, Ser.No. 556,206 9 Claims. (Cl. 317-234) This invention relates to a pressuremultiple electrical contact assembly suitable for use in compressionbonded electrical devices.

An object of this invention is to provide a pressure multiple electricalcontact assembly for electrical devices wherein an electrical connectionis made to each of at least two contact surfaces of a mesa-typesemiconductor element and at least one of the electrical connectionsincorporates a stress relief member to reduce the stresses caused bythermal changes within the electrical device.

Another object of this invention is to provide a pressure multipleelectrical contact assembly which distributes the force applied to thecontact assembly uniformly over the mesa-type configuration surfaces ofsemiconductor elements in physical contact with the contact assemblywhile providing electrical contact means to each surface of themesa-type configuration as required and at least one of the electricalcontact means incorporates a means for reducing the effects of thermalstressing within the electrical contact means.

Other objects of this invention will, in part, be obvious and will, inpart, appear hereinafter.

In order to more fully understand the nature and objects of thisinvention, reference should be had to the following description anddrawings, in which:

FIGURE 1 is a top view of a partially deformable cushioning memberembodying the teachings of this invention;

FIG. 2 is a side view, partially in cross-section, of a portion of anelectrical contact assembly employing the partially deformablecushioning member of FIGURE 1;

FIG. 3 is a side view, partially in cross-section, of another portion ofan electrical contact assembly employing the partially deformablecushioning member of FIG- URE 1;

FIG. 4 is a side view, partially in cross-section; of a portion of acompression bonded electrical device employing the portions of theelectrical contact assembly of FIGS. 2 and 3;

FIG. 5 is a top view of the semiconductor element employed in the deviceshown in FIG. 4; and

FIG. 6 is a side view, partially in cross-section, of a compressionbonded electrical device employing the portion of the compression bondedelectrical device shown in FIG. 4.

In accordance with the present invention and in attainment of theforegoing objects, there is provided a pressure multiple electricalcontact assembly comprising a partially deformable cushioning memberhaving two major opposed surfaces, the member having a plurality ofapertures, each aperture extending completely between the opposedsurfaces, at least two electrical contacts, each contact being threadedthrough a separate portion of the plurality of apertures, at least onecontact having an integral expansion element contained therein, anelectrical lead affixed to the expansion element of each electricalcontact having an expansion element and and electrical lead afiixed toeach of the other electrical contacts.

In order to more fully describe this invention, and for no otherpurpose, a pressure multiple contact assembly having only two electricalcontacts, only one of which incorporates a stress relief member, will bedescribed as one illustrative example of the use of the contact assemblyin pressure electrical devices.

With reference to FIG. 1, there is shown a top view of a partiallydeformable cushioning member 12 embodying the teachings of thisinvention and particularly suitable for use in compression bondedencapsulated electrical devices.

The cushioning member 12 has a top surface 14 and a bottom surface 16.The member 12 has a plurality of apertures 18, 26, 22, 24, 26 and 28extending between surface 14 and surface 16 disposed therein.

The cushioning member 12 consists of a material which can be partiallydeformed to match or compensate for any unevenness in any surface whichcomes in contact with the surfaces 14 and 16 of the member 12.

The material of the member 12 has properties which will allow it to coldflow under pressure. The cold flow proceeds only to a given limit andthen essentially ceases, whereupon the member 12. acts as a rigidmember.

Upon assuming the property of a rigid member, the material of the member12 then transmits the applied force without any further appreciablerestrictive cold flowing occurring. During operation of an electricaldevice at a temperature level as high as 200 C. to 250 C. but preferablylower and a pressure preferably exceeding 800 pounds per square inch,the allowable further deformation of a member 12 is as little aspossible in order to protect the functional reliability of theelectrical device in which the member 12 is utilized.

Preferred materials having the desired properties mentioned above arepolytetrafluoroethylene and trifiuoromonochloroethylene. These twomaterials in addition to having the desired properties, also are goodelectrically insulating materials for the operating range of devices upto approximately 250 C.

With reference to FIG. 2, a first electrical metal contact 30 isthreaded through apertures 18, 20, 22 and 24 of the member 12. Althoughthe contact 30 may have any desirable cross-sectional geometric shape, arectangular or square metal strip is preferred for use in compressionbonded electrical devices. The flat surfaces of the contact 30 providesa better distribution of forces and also provides a large electricalcontact surface area.

The contact 30 comprises a metal selected from the group consisting ofcopper, gold, nickel, silver, tin, indium and base alloys thereof.

The contact 30 is formed in a manner which allows those portions of thecontact 36 in contact with the sur' faces 14 and 16 to be flat, parallelto, and touching, the respective surfaces of the member 12. Thisconfiguration for the contact 30 permits handling of the assemblywithout fear of the contact 3% dropping out of the member 12.

An integral expansion portion 32 is provided in the contact 36 to allowfor the restricted flowing of the material comprising the member 12 andto compensate for any thermal and mechanical stresses which may occur inthe contact 30. An electrical lead 34 is affixed to the expansionelement 32 to provide a means to connect the contact 30 to an electricalsystem external to the assembly.

With reference to FIG. 3, there is shown a second metal electricalcontact 36 threaded through apertures 26 and 28. The preferredcross-section of the contact 36 is square or rectangular. The contact 36comprises a metal selected from the group consisting of copper, gold,nickel, silver, tin, indium and base alloys thereof.

Like the first contact 30, the contact 36 is formed so that the portionsof the contact 36 in contact with the surfaces 14 and 16 lie flat,parallel to, and touching, the respective surfaces of the member 12.This configuraof gold, silver, tin, .then be disposed between, -coatedsurface 48 and the electrical contact60 Without employing a bondingmaterial toform a permanent joint between the components.

3 tion prevents the contact 36 from falling out of the member 12 duringany handling and also provides a large electrical contact surface areafor connecting to an electrode. Anelectrical lead 38 is affixed to oneend efthe contact 36 to provide-a meansfor connecting'the contact-36into a remote electrical system.

With reference to FIG. 4, there is shown a portion of acompressionbonded semiconductor device utilizing the teachings of thisinvention.

The portionof the device is comprised of an electrically and thermallyconductive support member 42, made of a metal selected from the groupconsisting-of copper, silver, aluminum,-base alloys thereof-and ferrousbase alloys. Copper and brass, a-base alloy of copper, 'have been-foundparticularly satisfactory for this purpose.

The support member 42 has a peripheral flange 44 and an upwardlyextending pedestal portion 46. The upwardly extending pedestal portion46'has an uppermost mounting surface 48. Theperipheral flange 44hasa-top surface 50 and the upwardly extending pedestal portion 46 has aperipheral side surface 52.

An upwardly extending hollow cylindrical member 54 is affixed tothesupport member 42. The inner periphery of the member 54 conforms totheperipheral surface 52 of the pedestalportion .46. Themember54 isafiixed to thesupport member. 42 byany suitable means 'knownto thoseskilled in the art, such, for example, as .by disposing a suitable brazematerial 56 between the topsurface i) ofthe fiange44 and the sidesurface 52 of the pedestal portion.4.6 and aportion of the innerpheriphery and all of the bottom of the cylindrical mem- The cylindricalmember 54 is preferably made of a *ferrousbaeematerial althoughothersuitable materials,

aluminum. The layer 58 simultaneously compensates for any surfaceirregularities which may occur on the .surface 48 andthe mating surfaceof. an electrical contact6t The layer 58 may be disposed uponthe surface43 by any suitable means known to those skilled in the ,art, such, forexample, as electrodeposition-means, or as apreformed disc of, asuitable metal affixed to the surface ;.48 and then contoured tospecific requirements.

Anothersuitable method of disposing anequivalent non-reactive, malleableelectrically and thermally conductive structure in lieu of the layer.58is to coat the .surface 48 with a suitable material to promoteelectrical andthermal conductivity by such suitable means such,

for example, as electro-deposition. A metal member comprisinga metalselectedfrom the group consisting indium, lead and aluminum may and incontact with, the

The electrical contact 60 comprisesa metal, such for example, asmolybdenum, tungsten, tantalum and combinations andbase alloys thereof.The contact 60 may also be plated with a suitable material such, forexample, as gold.

The contact 60 is a firm supporting structure for a body ofsemiconductor material. The contact 60 should therefore have goodelectrical and thermal conductivity properties and a thermal expansioncharacteristic closely matched to the material comprising the body-ofsemiconductor material disposed on the contact 60.

A semiconductor element 62 is disposed on the electrical contact 60. Thesemiconductor element 62 comprises a body of a semiconductor materialselected from the group consisting of silicon, silicon carbide,germanium, compounds of Group III and Group V ele- The semiconductorelement 62 has a mesa-type structure, or multi-level .electrical contactsurfaces. An elec trical contact area 64, with a shape as shown in FIG.5,

isdisposed on, and in an electrically conductive relationship with theregion61 of semiconductivity. A second electrical contact area 66-isdisposed on, and in an electrical conductive relationship with theregion 65 of semiconductivity. Theelectrical contact-area 64 ofthiselement-62 is at a-higher elevation'than'the electrical contact area 66.The contactareas 64 and 66 are also physically separated from eachother.

The element 62 is-afiixed to the contact 60 by suitable means such, forexample, as by employing a solder layer 68 of an alloy of silver, leadand antimony.

Referring againto FIG. 4, the electrical contacts 30 and -36assembled-inthe member 12 is disposed on the semiconductor eleme'ntxiZ. The firstelectrical contact 30 is aligned, and is in electrical contact, .withthe electrical contact164. At the same ti1ne, the second electricalcontact --36 is simultaneouslyaligned, and'is in electrical contact,with the other electrical contact .66. Alignment of .the contacts and.36 vwith the respective ohmic contacts;64 Iand 6,6 is relativelysimple. The thickness of the cushioning member 12 is thin enough,approximately 15 mils,.so.that.t he member .12 is translucent. One istherefore able to orient the electrical contacts 30 and 36,withtherespective ohmic contacts64 and 66 on the surface of. theelement'62 quitev easily by.visual means only.

FIG. 4 is also-illustrative of the deformation of'the cushioning member12. The memberlZ partially deforms under the required force necessary tokeep the contacts 30 and 36 and the respective contacts 64 and 66 of theelement;62, as well as the element-62, the contact 60 and the supportmember42 in an electrical and thermal conductivity relationship. Thisrequired force causes the material comprising the cushioning member 12to flow .whereby the member 12 molds itself. to conform to the surfaceirregularities of the element Y62 and its electrical contacts 64 and 66as Well as at least partially filling the apertures present within themember 12 and thervoids existing between the assembled. components ofthe electrical device immediately adjacent to the member 12.

With reference to FIG. 6, there is shown a compression bonded electricaldevice 70 which incorporates the structure of the portion of theelectrical device shown in FIG. 4.

consisting of ceramic, mica, glass, quartz and fluorocarbon.

A first a-pertured metal thrust washer 74 is disposed about theelectricalconductors '34 and 38 upon the top surface of the aperturedinsulating washer 72. At least one apertured metalspring washer 76 isdisposed about the electrical conductors 34 and 38 upon the top surfaceof the thrust washer 74.

A second apertured metal thrust washer 78, similar to, or the same as,the washer 74 is disposed on the uppermost spring washer 76.An-apertured expandable metal retaining ring 80, similar to a snap ring,is disposed about the electrical conductors 34 and 38 within, and isretained wardly extending cylindrical member- 54.

The ring 80 cooperating with the cylindrical member 54 and acting on thethrust washer 78 resiliently urges the apertured spring washer 76 totransmit a compression force through the apertured thrust washer 74 andthence through the apertured electrically insulating washer '72 to forcethe electrical contacts 30 and 36, the semiconductor element 62, theelectrical contact 66 and the uppermost mounting surface 48 of theupwardly extending pedestal portion 46 of the support member 42 into afirm, intimate, electrically conductive relationship with each other.

More than one apertured spring washer 76 of the same, or differentthickness, may be required to cooperate with the retaining ring 80 andthe cylindrical member 54 to create the necessary compressional forcerequired for a reliable operating device 76.

An electrically non-conducting washer 84 is disposed on the retainingring 80. The washer 84 has a plurality of apertures 86. Each of theleads 34 and 38 project through an individual aperture 86 of the washer84. The washer 84 limits the lateral movement of the leads 34 and 38thusly reducing the associated stresses resulting from the movement fromdeleteriousl-y affecting the joints between the contacts 30 and 36 andthe respective leads 34 and 38.

A molecular sieve 88 is disposed on the washer 84. The sieve 88 has anaperture 99 through which the leads 34 and 38 project. T e sieve 88 isself-centered since its outer peripheral side surface 92 conforms to theinner wall of the member 54. The sieve 88 functions as amoisturegettering device.

The device 70 is completed by providing a hermetic enclosure for thesemiconductor wafer 62. The hermetic enclosure is formed by aflixing anapertured header assembly 94 to the member 54. The header assembly 94comprises an outwardly extended flanged member 96 affixedto a multipleapertured insulating seal member 98.

The header assembly 94 is joined to the member 54 by welding theoutwardly extended flanged member S t; to an integral annular weld ring160 formed within the member 54. An upwardly extending integral flange192 of the member 54 acts as a guide for positioning the header assembly94 during assembly and joining operations.

The electrical lead 34 passes through a metal sleeve 104 in one of theapertures of the header assembly 94. A hermetic seal is achieved bycompressing the sleeve 104 by any suitable means, such, for example asby swaging, rolling and the like, about the portion of the outerperiphery of the lead 34 which it encompasses.

The electrical lead 38 terminates in an electrical connector 106hermetically sealed into the header assembly 94. To electrically connectthe lead 38 into an external system, another electrical lead 108,suitably aflixed to the connection 106, is required.

An electrical contact and thermal dissipating stud 110 is either affixedor is integral with the support member 42. The stud 110 is used toconnect the support member 42 to an electrical conductor and heat sink.

The following example is illustrative of the teachings of thisinvention:

A good electrically and thermally conductive support member having anintegral electrical contact and thermal dissipating stud was preparedfrom a piece of copper alloy bar stock. The finished machinedconfiguration was the same as illustrated in FIG. 6. A layer of silverwas then aflixed to the uppermost mounting surface of the pedestalportion and machined to a specific flatness and diameter.

A ferrous integral case and weld ring assembly was then affixed to thesupport member by disposing a layer of braze material between portionsof the assembly and the top of the peripheral flange and the sidesurface of the upwardly extending pedestal portion.

A silicon semiconductor transistor element suitable for use as acompression bonded electrical device was prepared. The element had a topsurface which had been divided into two separate distinct regions ofsemiconductivity. The electrical contact to one semiconductivity regionwas 0.5 mils higher than the electrical contact to the other region ofsemiconductivity.

The semiconductor element was affixed to a molybdenum electrical contactby disposing a layer of a silverlead-antimony alloy electrical soldermaterial between the bottom surface of the element and the top surfaceof the contact. The element and contact, aflixed to each other, was thendisposed within the integral case and weld ring assembly and upon thelayer of silver on the pedestal.

A polytetrafluoroethylene cushioning member was prepared. The member wasabout 15 mils in thickness and large enough to cover the entire surfaceof the semiconductor element. Apertures were formed entirely through thethickness of the member.

A piece of flat silver metal ribbon was threaded through one series ofapertures in the cushioning member. A flat tab was formed at thebeginning end of the ribbon pressed against the top surface. The ribbonpassed down through one aperture and was flattened against the bottomsurface of the cushioning member for the entire length to the nextaperture. The ribbon transversed the aperture and was formed intoapproximately a semicircular stress relief loop and passed downwardlythrough the next aperture. The ribbon was then flattened against thebottom surface of the cushioning member to the next aperture. The ribbonthen passed upwardly through this next aperture and the end of theribbon was formed flat along the top surface of the cushioning member.

Another piece of flat silver metal ribbon, shorter than the first pieceof metal ribbon, was then threaded to the next series of apertures inthe cushioning member. A flat tab was formed at one end of the ribbonand the rest of the ribbon was threaded downwardly through one apertureuntil the flat tab was lying flat on the top surface of the cushioningmember. The ribbon was then formed flat against the bottom surface ofthe cushioning member to the next aperture in the series. The ribbon wasthen passed upwardly through the aperture and the end of the ribbon wasformed into a flat tab along the top surface of the cushioning member.

A first silver electrical lead was aflixed to the stress relief loop ofthe first piece of silver ribbon. A second silver electrical lead wasaflixed to a tab of the second silver electrical lead, the tab beingclosest to the center of the cushioning member.

The resulting structure was the pressure multiple contact assembly shownin FIGS. 1, 2 and 3.

The contact assembly was then disposed within the integral case and weldring assembly and positioned on top of the semiconductor element. Thecushioning mem ber was translucent enough to allow the positioning ofthe silver metal ribbon electrical contacts on the two aluminumelectrical contacts of the semiconductor element.

An apertured ceramic washer was then placed over the silver electricalleads and disposed on the top surface of the cushioning member. Theouter periphery of the mica washer conformed with the inner periphery ofthe integral case and weld ring assembly.

A first steel apertured thrust washer was then disposed about theelectrical conductors from the contact assembly and on top of theceramic washer. The outer periphery of the thrust washer conformed tothe inner periphery of the integral case and weld ring assembly. Twoapertured steel spring washers and a second steel thrust washer wererespectively then disposed about the electrical conductors from theelement and on top of the first steel thrust washer. The outer peripheryof the spring washers and the second steel thrust washer conformed tothe inner periphery of the integral case and Weld ring assembly.

Force was then applied to the second steel thrust washer and a steelretaining ring was snapped into an annular groove in the integral caseand Weld ring assembly to keep the spring washers in compression. Thetheoretical pressure on,the surface of the element was in excess of 800p.s.i. based on anabsolutely smooth surface.

An apertured polytetrafluoroethylene washer was disposed ontopof thesteelretaining ring. The silver electricalleads passed throughtherespective apertures of the washer. The outer periphery of the washerconformed to the inner periphery of the case and weld ring assembly.

After one hour,,the polytetrafluoroethylene washer retainingringwasremoved and the device was unloaded.

The pressure multiple contact assembly was removed from the device,Examination of the polytetrafluoroethylene cushioning memberrevealedthat the member had cold flowedunder pressure and molded itselfabout the irregularities in the surface of and portions of theelectrical contacts on the element. An outline of the struc .ture of theelement wasclearly impressed in the surface of the member. Thesurfacesof the member had also molded themselves flush with the ribbon contactscontained therein. The semiconductor element, upon visual inspection,was still structurally satisfactory.

Thedevice was reloaded except for a hermetic seal.

The calculated pressure on the theoretically smooth surface area of theelement ,was approximately 102.0 p.s.i.

The device was heated to a temperature of about 200 C. for a period of68 hours. The device was then cooled, the retaining ring I andpolytetrafiuoroethylene washer removedand the pressure rnultipleelectrical contact assembly removed for an examination.

[The cushioning member of the contact assembly had been permanentlydeformedabout 10%. The outline of thesemiconductor elements surface andportions of the electrical contacts attached thereto was clearlyembossed in the surface of the cushioning member. The surfaces of thememberwere still molded flush-with the ribbon contacts containedtherein. Visual examination of the semiconductor .element showed nodefects.

The device was reloaded again except for a hermetic seal. A new pressuremultiple electrical contact assembly was substituted for the permanentlydeformed assembly previously used. The pressure applied to the semicon-.ductor element surface was a calculated 1400 psi. The

device was heatedto ateunperature of 200 C. and held .at temperature forapproximately two hours. The device wasfthen cooled, the retainingringand the polytetrafluoroethylene washer were removed and the pressuremultiple electrical contact assemblyremoved for examination.

The thrust memberhad been permanently deformed approximately 10%.1Th'estructure ofthe semiconductor .element and portions ofthe electricalcontact-s attached ,thereto was again clearly embossed in thesurface ofthe .thrust, member. Visual examination of, the semiconductor ,element,stillrevealed no damage. to the element.

" Employing a new polytetrafluoroethylene thrust member, "mils inthickness, the device was again reassembled A calculated pressure of1000 p.s.i. Was impressed on the surface. of the semiconductor element.An aperturedmolecularsieve was disposed about electrical leadsconnected. tothe pressure multiple electrical contact assembly and onthe polytetrafluoroethylene washer. The hermetic enclosure shown in FIG.5 was attached to the integral case and weld ring assembly to form acomplete electrical device within which the semiconductor element washermetically sealed.

The hermetically sealed electrical device was then electrically' cycledthrough a theoretical operating cycle, typical of what the device wouldencounter during normal usage. The device continually performedsatisfactorily andwell within its design limits.

The device was carefully disassembled and the pressure multipleelectrical contact assembly was examined.

The polytetrafluoroethylene cushioning member had been permanentlydeformed about 10%. The member had molded itself about all the surfaceirregularities which .had been in contact with the member. The stressrelief portion of the one silver metal ribbon had been deformed slightlyby the movement of thecushioning member, but theelectrical lead wasstill firmly attached tothe stress relief portion. i

A visual examination of .the semiconductor element showed the element tobe still in satisfactorylcondition.

It was also noted that during all these tests and evaluations, theapertured polytetrafiuoroethylene wlasher ,reduced the accidentalfracturing of the slender silver electrical leads to the pressuremultiple contact assembly. The washer had reduced considerably thelateral movement of the slender electricalleads.

A trifluoromonochloroethylene cushioning member and an aperturedtrifluoromonochloroethylene wlasher were employedin the same type ofelectrical devices in lieu of their polytetrafluoroethylenecounterpartsnEqual- 1y satisfactoryresults were obtained-when the sametests were repeated using these substitutedmaterials.

Although the member 12 haslbeen described as being a circular disk,other geometrical shapes may;-be employed as configurations for themember 12 and will Work equally as well. The geometrical shape requiredis'determined only by the encapsulating member components, andparticularly the design of the semiconductor element employed therein,as well asthe number, and type, of electrical connections required to be,made to' the wafer.

While the invention has been described withreference to particularembodiments and examples, it will be understood of course, thatmodifications, substitutions and the like may be made therein withoutdeparting from its scope.

We claim as our invention:

1. A pressure multiple electrical contact assernbly comprising (1) apartially deformable cushioning member having two major opposedsurfaces, the member having a plurality of apertures, each apertureextending completely between the opposed surfaces, (2) at least twoelectrical group consisting of polytetra-fiuoroethylene and trifluo romonochloroethylene.

3. The pressure multiple electrical contact assembly of claim 1 in whichthe material comprising the electrical contacts is at least one metalselected from the group consisting of copper, gold, nickel, silver, tin,indium and base alloys thereof.

4. The pressure multiple electrical contact assembly of claim 1 in whichthe material comprising the partially deformable cushioning member isone selected from the group consisting of polytetrafluoroethylene andtrifluoromonochloroethylene and the material comprising the electricalcontacts is at least one metal selected from the group consisting ofcopper, gold, nickel, silver, tin, indium and base alloys thereof.

5. The pressure multiple electrical contact assembly of claim 1 in whichthe material comprising the partially deformable cushioningmember is oneselected from the group consisting of polytetrafluoroethylene andtrifluoromonochloroethylene and the material comprising the electricalcontacts is silver.

'6. A'semiconductor device comprising (1) a semiconductor element havingat least two electrical contacts affixed to one major surface of theelement (2) a pressure multiple electrical contact assembly inelectrical contact with each electrical contact on the one major surfaceof the element, the assembly comprising a partially deformablecushioning member having two major opposed surfaces, the member having aplurality of apertures, each aperture extending completely between theopposed surfaces, at least two electrical contacts, each electricalcontact being threaded through a separate portion of the plurality ofapertures, each of the electrical contacts being in electrical contactwith an electrical contact afiixed to the semiconductor element, atleast one of the contacts having an integral expansion element containedtherein, the electrical contacts each comprising a metal selected fromthe group consisting of copper, gold, nickel, silver, tin, indium andbase alloys thereof, an electrical lead affixed to the expansionelements of each electrical contact having an integral expansion elementand an electrical lead afiixed to each of the other electrical contacts,(3) a means for applying a constant force on the pressure multipleelectrical contact assembly whereby each of the electrical contacts ofthe pressure multiple electrical contact assembly are maintained inthermal and electrical conductive relationship with each respectiveelectrical contact aflixed to the semiconductor element.

7. The semiconductor device of claim 6 in which the material comprisingthe partially deformable cushioning member is one selected from thegroup consisting of polytetrafiuoroethylene andtrifluoromonochloroethylene.

8. The semiconductor device of claim 6 in which the material comprisingthe partially deformable cushioning member is one selected from thegroup consisting of polytetrafluoroethylene andtrifluoromonochloroethylene and each electrical contact of the pressuremultiple electrical contact assembly is made of silver.

9. The semiconductor device of claim 6 in which an aperturedelectrically non-conducting member is disposed on the means for applyinga constant force on the pressure multiple electrical contact assembly,the apertured member restricting the lateral movement of an electricallead passing through an aperture of the member.

References Cited UNITED STATES PATENTS 2,728,881 12/1955 Jacobi 317-2343,059,157 10/1962 English et al 317-234 3,296,501 1/1967 Moore 317-234JAMES D. KALLAM, Primary Examiner. R. F. POLISSACK, Assistant Examiner.

1. A PRESSURE MULTIPLE ELECTRICAL CONTACT ASSEMBLY COMPRISING (1) APARTIALLY DEFORMABLE CUSHIONING MEMBER HAVING TWO MAJOR OPPOSEDSURFACES, THE MEMBER HAVING A PLURALITY OF APERTURES, EACH APERTUREEXTENDING COMPLETELY BETWEEN THE OPPOSED SURFACES, (2) AT LEAST TWOELECTRICAL CONTACTS, EACH ELECTRICAL CONTACT BEING THREADED THROUGH ASEPARATE PORTION OF THE PLURALITY OF APERTURES, (3) AT LEAST ONE CONTACTHAVING AN INTEGRAL EXPANSION PORTION CONTAINED THEREIN, (4) ANELECTRICAL LEAD AFFIXED TO THE EXPANSION ELEMENT OF EACH ELECTRICALCONTACT HAVING AN INTEGRAL EXPANSION ELEMENT, AND (5) AN ELECTRICAL LEADAFFIXED TO EACH OF THE OTHER ELECTRICAL CONTACTS.